In order to reduce its
carbon footprint, the steel industry is testing new technologies that don’t
rely on fossil fuels.
Top:
Tapping Boston Metal’s semi-industrial molten oxide electrolysis cell. Visual:
Boston Metal
IN THE CITY of Woburn,
Massachusetts, a suburb just north of Boston, a cadre of engineers and
scientists in white coats inspected an orderly stack of brick-sized,
gunmetal-gray steel ingots on a desk inside a neon-illuminated lab space.
What they were looking at was a batch of steel created using an
innovative manufacturing method, one that Boston Metal, a
company that spun out a decade ago from MIT, hopes will dramatically reshape
the way the alloy has been made for centuries. By using electricity to separate
iron from its ore, the firm claims it can make steel without releasing carbon
dioxide, offering a path to cleaning up one of the world’s worst industries for
greenhouse gas emissions.
An essential input for engineering and construction, steel is
one of the most popular industrial materials in the world, with more than 2 billion tons produced annually. This
abundance, however, comes at a steep price for the environment. Steelmaking
accounts for 7 to 11 percent of global greenhouse-gas
emissions, making it one of the largest industrial sources of atmospheric
pollution. And because production could rise by a third by 2050, this
environmental burden could grow.
That poses a
significant challenge for tackling the climate crisis. The United Nations says significantly
cutting industrial carbon emissions is essential to keeping global warming
under the 1.5 degrees Celsius mark set under the 2015 Paris climate agreement.
To do so, emissions from steel and other heavy industries will have to fall by
93 percent by 2050, according to estimates by the International Energy
Agency.
Facing escalating pressure from governments and investors
to reduce emissions, a number of steelmakers — including both major producers
and startups — are experimenting with low-carbon technologies that use hydrogen
or electricity instead of traditional carbon-intensive manufacturing. Some of
these efforts are nearing commercial reality.
“What we are talking about is a capital-intensive, risk-averse
industry where disruption is extremely rare,” said Chris Bataille, an energy
economist at IDDRI, a Paris-based research think tank. Therefore, he added,
“it’s exciting” that there’s so much going on all at once.
Still, experts agree that transforming a global industry that
turned over $2.5 trillion in 2017 and employs more
than 6 million people will take enormous
effort. Beyond the practical obstacles to scaling up novel processes in time to
reach global climate goals, there are concerns about China, where over half the
world’s steel is made and whose plans to decarbonize the steel sector remain
vague.
“It’s certainly not an easy fix to decarbonize an industry like
this,” said Bataille. “But there’s no choice. The future of the sector — and
that of our climate — depends on just that.”
MODERN
STEELMAKING INVOLVES several production stages. Most commonly, iron ore is
crushed and turned into sinter (a rough solid) or pellets. Separately, coal is
baked and converted into coke. The ore and coke are then mixed with limestone
and fed into a large blast furnace where a flow of extremely hot air is
introduced from the bottom. Under high temperatures, the coke burns and the
mixture produces liquid iron, known as pig iron or blast-furnace iron. The
molten material then goes into an oxygen furnace, where it’s blasted with pure
oxygen through a water-cooled lance, which forces off carbon to leave crude
steel as a final product.
This method, first patented by English engineer Henry Bessemer
in the 1850s, produces carbon-dioxide emissions in different ways. First, the
chemical reactions in the blast furnace result in emissions, as carbon trapped
in coke and limestone binds with oxygen in the air to create carbon dioxide as
a byproduct. In addition, fossil fuels are typically burned to heat the blast
furnace and to power sintering and pelletizing plants, as well as coke ovens,
emitting carbon dioxide in the process.
As much as 70 percent of the world’s
steel is produced this way, generating nearly two tons of carbon dioxide for
each ton of steel produced. The remaining 30 percent is almost all made
through electric arc furnaces, which use an electrical current to melt steel —
largely recycled scrap — and have far lower CO2 emissions than blast
furnaces.
“It’s certainly not an easy fix to decarbonize an industry like this,”
said Bataille. “But there’s no choice. The future of the sector — and that of
our climate — depends on just that.”
But because of the limited scrap supply, not all future demand
can be met this way, said Jeffrey Rissman, an industry program director and
head of modeling at the San Francisco-based energy and climate policy firm
Energy Innovation. With the right policies in place, recycling could supply up
to 45 percent of global demand in 2050, he said. “The rest will be satisfied by
forging primary ore-based steel, which is where most emissions come from.”
So “if the steel industry is serious” about its climate commitments,
he added, “it will have to fundamentally reshape the way the material is made —
and do so fairly quickly.”
ONE
ALTERNATIVE TECHNOLOGY being tested replaces coke with hydrogen. In Sweden, Hybrit —
a joint venture between the steelmaker SSAB, the energy supplier Vattenfall, and
LKAB, an iron ore producer — is piloting a process that aims to repurpose an
existing system called direct reduced iron. The process uses coke from fossil
fuels to extract oxygen from iron ore pellets, leaving a porous iron pellet
called sponge iron.
The Hybrit method instead extracts the oxygen using fossil-free
hydrogen gas. The gas is created through electrolysis, a technique that uses an
electric current — in this case, from a fossil-free energy source — to separate
water into hydrogen and oxygen. (Most pure hydrogen today is made with
methane, which produces CO2 when burned.) The resulting sponge iron then goes
into an electric arc furnace, where it’s eventually refined into steel. The
process releases only water vapor as a byproduct.
“This technology has been known for a while, but it’s only been
done in the lab so far,” said Mikael Nordlander, head of industry
decarbonization at Vattenfall. “What we are doing here is to see if it can work
at [the] industrial level.”
Last August, Hybrit reached its first milepost: SSAB, which
produces and sells the end product, delivered its first batch of fossil-free steel to
the automaker Volvo, which used it in vehicle prototypes. It is
also planning a plant for commercial-scale production, which it aims to
complete by 2026.